An organic EL device comprises a pair of electrodes (anode and cathode) and a light-emitting layer disposed between the electrodes. Upon application of voltage to the pair of electrodes, hole injection from the anode and electron injection from the cathode take place, and these holes and electrons bind to each other in the light-emitting layer such that the organic EL device emits light.
One of the pair of electrodes is composed of an optically transparent electrode. Light generated in the light-emitting layer outgoes through the optically transparent electrode. Currently, an indium tin oxide (abbreviated to ITO) thin film is frequently used in this optically transparent electrode.
Since the ITO thin film has a higher refractive index than that of the light-emitting layer or the like, total reflection occurs at the interface of the ITO thin film. Therefore, the most part of light emitted from the light-emitting layer does not outgo and is thus used ineffectively under present circumstances. Thus, for suppressing total reflection by means of a smaller angle of incidence on the electrode (ITO thin film), a method for producing an organic EL device has been proposed, which comprises forming, in an electrode or a light-emitting layer, a diffraction grating by which a traveling direction of light emitted from the light-emitting layer is changed (see e.g., PATENT DOCUMENT 1).
The organic EL device comprises, in addition to the pair of electrodes in a layer form and the light-emitting layer, predetermined organic or inorganic layers, if necessary, between the pair of electrodes and is prepared by stacking this plurality of layers in order on a support substrate. In the method for producing an organic EL device as the conventional art, the organic EL device is prepared by forming a curable resin layer having asperities formed on the surface, on a transparent support substrate and then stacking a plurality of layers in order on this curable resin layer by, for example, a deposition or sputtering method. The plurality of layers can thus be stacked in order on the curable resin layer having asperities formed on the surface to form, on the plurality of layers, a structure with asperities that functions as a diffraction grating.